This invention relates to a novel class of prostanoic acid derivatives, to a method of treating peptic ulcer disease, and to pharmaceutical compositions containing these derivatives.
It is known that certain prostaglandins have been found to be useful in the treatment of peptic ulcer disease. It is further known that a specific class of these prostaglandins, namely tetraenyl, 16-hydroxy prostaglandins which are represented by the following structural formula ##STR2## wherein R represents hydrogen or lower alkyl having 1 to 6 carbon atoms; R.sub.1 represents vinyl, or lower alkyl having 1 to 4 carbon atoms and the wavy line represents R or S stereochemistry; R.sub.2, R.sub.3 and R.sub.4 are hydrogen or lower alkyl having 1 to 4 carbon atoms or R.sub.2 and R.sub.3 together with carbon Y form a cycloalkenyl having 4 to 6 carbon atoms or R.sub.3 and R.sub.4 together with carbons X and Y form a cycloalkenyl having 4 to 6 carbons have potent gastric antisecretory and cytoprotective properties which makes them effective in the treatment of peptic ulcer disease. These compounds are described further in U.S. Pat. No. 4,683,328.
Applicants have discovered that certain 16-alkyl tetraenyl prostanoic acid derivatives which are represented by formula I function as in vivo precursors or pro drugs of the aforementioned 16-hydroxy tetraenyl prostanoic acid derivatives which are represented by formula IV (Scheme A). In order for the compounds of formula I to exert their antisecretory and cytoprotective properties they must be "transformed" into the active species which are represented by formula IV. This "transformation" takes place in an acidic medium. Thus the pro drugs must be administered by a method that would allow for exposure to said condition.